CM8001

Styrofoam is made up of polystyrene foam. When the polystyrene dissolves in the acetone, the air in the foam is released, causing it to look like you’re dissolving this massive quantity of material into a small volume of liquid.

a)LDPE cannot be used in this application because it does not have the required strength.

b) The molecules of HDPE must line up in a way that produces the required strength. Using a thin liner of HDPE allows sufficient flexibility

When the piece of plastic is stretched, the strip narrows and “necks down.” The molecules become aligned parallel to each other and in the direction of the pull. This alteration of the three-dimensional structure is not reversible, and if the pulling continues, the plastic breaks. When the same pulling force is applied to a piece of paper, the paper tears rather than stretching to any significant extent. The cellulose molecules in paper are held far more rigidly in place, and are not free to become aligned.

4a) 1.Stable over time intended use 2. Non-toxic 3.Low Cost 4.Lack of solubility in body fluid.

4b)Several different types of contact lenses on the market and each uses different type of polymer.

Soft contacts are made of pliable hydrophilic (“water-loving”) plastics called hydrogels. Hydrogels absorb significant amounts of water to keep the lenses soft and supple.

Desirable properties include being nontoxic, permeable to oxygen, comfortable to wear, and inexpensive. Also desirable is the ability to conform to the shape of the eye and to be easily cleaned (if not disposable)

4c) As mentioned in the previous part, hard contact lenses are typically made of PMMA, a rigid non-gas permeable plastic. The soft contact lenses that replaced them are made of silicone, which is flexible and allows oxygen to reach the eye. Because of these properties, the soft lenses tend to be more comfortable